Marihuana (delta 9-THC) has been reported to produce hypothermia in many species, including man. Studies designed to elucidate the cerebral site of action of delta 9-THC will be carried out in chronic unanesthetized cats. In vivo and in vitro experiments with mice will be continued to study the physiological and biochemical changes induced by delta 9-THC and the effect on these changes of pretreatment with agents which alter neurotransmitter mediated responses. The cardiovascular actions of delta 9-THC appear to arise through alteration of central sympathetic outflow. Sympathetic outflow from cardiac and mesenteric nerves will be monitored in cats before and after delta 9-THC administration. The effect of altered plasma sodium levels on the hypothermic response to delta 9-THC will be studied. BIBLIOGRAPHIC REFERENCES: Haavik, C. O. and Hardman, H. F.: Cannabis and thermoregulation. In Drugs and Body Temperature, P. Lomax and E. Schombaum, ed., Marcel Dekker, In press, 1977. Haavik,C.O.: Profound hypothermia in mammals treated with tetrahydrocannabinols, morphine, or chorpromazine. In Drugs and Hypothermia, Symposium, Chairman A. J. Karow, Fed. Proc. In Press, 1977.